Heating water calculator

[Wonkydonkey]

Good afternoon,

As the title says, heating water. On this site (jims) there are some calculators. what I would like to know as there is no formula that i could see.
How does it take into account the surrounding temp. Ie, if it was windy, winter, summer or better still what insulation are you using and Do you have a lid on it.
We know that putting a lid on a pot enables it to boil quicker as there is less heat loss

So as I will be soon getting a 70lt thermo pot, converting it. I would be boiling no more than 60lt as far as I can see the calculator does not really help me make a clear choice of an element.
I have read a few posts about converting a thermo pot but I have not seen much on boiling times

Ps, I was thinking of one of those 3kw pigtails. I don't really want to make 2 holes. Also I don't really want long 5kw-ish as I have no cooker point

I'm sure there's info out there, but trawling around and around, it seems easier to ask.

Thanks wonky

[thickodicko]

If anyone knows the answer to this it would help me out massively too!

I know Angel homebrew forum has some conversions but only what they have tested

[BenB]

It looks like they're not:

function temp(form)
{
var start = parseFloat(form.StartDegC.value, 10);
var end = parseFloat(form.EndDegC.value, 10);
var vol = parseFloat(form.Volume.value, 10);
var power = parseFloat(form.Power.value, 10);

var time = 0.0;
time =(4184.0 * vol *(end - start ))/ power / 1000.0 / 60.0 ;
form.Time.value = Math.round ( time + 0.5 );

They're just using the temperature differential required, the thermal capacity of water and the kWs of the heater IE it's a best case scenario with no heat loss. The thermal capacity of water is so high that insulation will only make a modest difference.

[BenB]

PS I would really consider having two elements. I know cutting two holes is a pain but it's a real pain if your one and only element gives up the ghost half way through a boil. Luckily when I lost an element it was in my two element boiler so I could limp on and still create beer. Don't forget we're giving the elements quite a hard time- constantly on for an hour or two....

If you're going to be boiling no more than 60 litres but could potentially be boiling 60L it will be worth having two elements. I've got 3kW and haven't gone over 30L and sometimes it's a bit tiresome waiting for a boil. Will you get a good enough boil for a good hot break with 3kW/60L?

Two 3kW elements would be my choice (one from an extension lead from another circuit).......

[Wonkydonkey]

Thanks for yor reply benb,

I do take your point. I have thought about it hard, very hard infact. I read about elements failing. Etc. but with abit of tlc, ie keeping the element clean. And also havining a spare to fit if the need arises, yes I can see it will be a faf emptying and fitting the new one.more than just switching on the other element. But making more holes than I really need does not appeal to me. I can at a later time make another hole, but I can't block it up that easy. If I move, and can upgrade to a bigger element, I think I think I could almost just take out the pig tail and cut a bigger hole in the same place.
There are other options, that I have not really looked into yet, one of them being one of those heaters that you just stick in from the top, Iike a wand
But like a asked up the top. it was the calculator and the time and heat loss, but asking about this I hoped someone would say read this post or I have done this It works.
I did read an old post somewhere, where aleman has converted a Thermopot, and someone asked someone else about boiling and if it was vigorous, 65lt was spoken time was not on the list, the reply was ok/fine.
But on another note the lead is also very important to get right. There's no point getting the wrong flex and wasting the electric heating a crap cable up.

But like I said earlier. I do take your point as a valid point.

Thanks
Wonky

Edit, maths not my strong point, and thanks for looking how it was calculated.

With the thermo pots you loose very little in the way of heat.
Edit no2....
http://www.thehomebrewforum.co.uk/showt ... hp?t=11537

I use an 80 litre one as a boiler.
It's great

[Wonkydonkey]

As I have been looking around and around, about Thermo conversions.

I came across an old post of aleman's he has the same element 3kw backer, he says 30Lt + takes about 40mins. And it did not matter that it was only just above freezing out side where he brews, it still worked as if it was summer outside

So the calc is right in the time, and thanks Benb for looking into it.

So I can carry on thinking how I'm converting the Thermo pot. By the way like I said before I will have two elements it's just that one will be still in a £5 asda kettel. As I'm going herms. And if I get on with the whole herms thing then I'll invest in a 6lt Thermo pot, just like aleman's.

[Andy]

Yup, the calculator is a theoretical one and just runs the maths assuming no losses anywhere. In reality though it's accurate enough